In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix OOBs when building SMB2_IOCTL request
When using encryption, either enforced by the server or when using
'seal' mount option, the client will squash all compound request buffers
down for encryption into a single iov in smb2_set_next_command().
SMB2_ioctl_init() allocates a small buffer (448 bytes) to hold the
SMB2_IOCTL request in the first iov, and if the user passes an input
buffer that is greater than 328 bytes, smb2_set_next_command() will
end up writing off the end of @rqst->iov[0].iov_base as shown below:
mount.cifs //srv/share /mnt -o ...,seal
ln -s $(perl -e "print('a')for 1..1024") /mnt/link
BUG: KASAN: slab-out-of-bounds in
smb2_set_next_command.cold+0x1d6/0x24c [cifs]
Write of size 4116 at addr ffff8881148fcab8 by task ln/859
CPU: 1 UID: 0 PID: 859 Comm: ln Not tainted 6.12.0-rc3 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
1.16.3-2.fc40 04/01/2014
Call Trace:
dump_stack_lvl+0x5d/0x80
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
print_report+0x156/0x4d9
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
? __virt_addr_valid+0x145/0x310
? __phys_addr+0x46/0x90
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
kasan_report+0xda/0x110
? smb2_set_next_command.cold+0x1d6/0x24c [cifs]
kasan_check_range+0x10f/0x1f0
__asan_memcpy+0x3c/0x60
smb2_set_next_command.cold+0x1d6/0x24c [cifs]
smb2_compound_op+0x238c/0x3840 [cifs]
? kasan_save_track+0x14/0x30
? kasan_save_free_info+0x3b/0x70
? vfs_symlink+0x1a1/0x2c0
? do_symlinkat+0x108/0x1c0
? __pfx_smb2_compound_op+0x10/0x10 [cifs]
? kmem_cache_free+0x118/0x3e0
? cifs_get_writable_path+0xeb/0x1a0 [cifs]
smb2_get_reparse_inode+0x423/0x540 [cifs]
? __pfx_smb2_get_reparse_inode+0x10/0x10 [cifs]
? rcu_is_watching+0x20/0x50
? __kmalloc_noprof+0x37c/0x480
? smb2_create_reparse_symlink+0x257/0x490 [cifs]
? smb2_create_reparse_symlink+0x38f/0x490 [cifs]
smb2_create_reparse_symlink+0x38f/0x490 [cifs]
? __pfx_smb2_create_reparse_symlink+0x10/0x10 [cifs]
? find_held_lock+0x8a/0xa0
? hlock_class+0x32/0xb0
? __build_path_from_dentry_optional_prefix+0x19d/0x2e0 [cifs]
cifs_symlink+0x24f/0x960 [cifs]
? __pfx_make_vfsuid+0x10/0x10
? __pfx_cifs_symlink+0x10/0x10 [cifs]
? make_vfsgid+0x6b/0xc0
? generic_permission+0x96/0x2d0
vfs_symlink+0x1a1/0x2c0
do_symlinkat+0x108/0x1c0
? __pfx_do_symlinkat+0x10/0x10
? strncpy_from_user+0xaa/0x160
__x64_sys_symlinkat+0xb9/0xf0
do_syscall_64+0xbb/0x1d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f08d75c13bb
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-28). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it